Process for the fibrous esterification of cellulose



Patented July 14, 1936 umrso OFFICE;

PROCESS FOR THE 'FIBROUS "E STERI'FI-- GATION OF CELLULOSECalrleJ.'Malm; Rochester, N.-Y., and Charles-Lt Fletcher, Kingspor-t;Tenn., c assignors to ,East-l. man {Kodak Company, Rochester, N.Y.;alcor-V poratioh. ,of New York Nd:Di'awi1ig-. Application May=:19;1933;\-

SerialNo. 671,901

9 Claims, (0]. 2602-101),

Theipresentinvention relatesto:a fibrous =proc-r ess of"esteriiyingl'cellulose-:1n which a; liquid sat-1 uratedrhydrocarborriis eemployedrr as: the? nonsolvent andtchlorinated:hydro'carbon.:isremployedaresuitablein:fibrouszesterificationrprocesses 'arer knowm under various:names :"suchas 1igroin,ii;pe-:= troleumr:ether;1Stoddard 'zsolvent,kerosene: gasoe 1ine,naphtha-, etc. 7 Stoddard 'solventuisaa commonly:knownzfaliphatic hydrocarbon? which? is 116- scribed'intfiBureaumfStandards 'BiiIIetin CS *3L28 (1929 )1: In .the=fibrous processeswherezsthese sat uratedarhsrdrocarbbns are! employed'sasethe none-.-

solventszc: in: the r esterifi'cation-w of cellulose the-e amounts:necessaryaofassure insolubility of the 1 resulting :esteriin'thefesterification *b'athare mu'chf less thanizisrthe casez'withthenon-solventsswhich are'vordinarilyf employed. However thesenonsolventsssuffer the disadvantage that their mixtures with 'the lowerfatty acids and anhydrides are heterogeneous especially in those caseswhere 4 hydro-carbons havingsta -hig'h#boiling range are I employedi 1O'ne object of 'our inventibn is to provide a proc-= ess for the fibrousesterificat-iozr =ofcellulose in which a saturated hydrocarbon may beempldyed as the non-solvent zand"yetithe bath is homoi geneousand fromwhich the-non=solvent and homogenizing'diduid may-be easily removedafter -1 the completion of 'theestrificationr Another ob' ject of ourinventibn is to "p- IOV-idanfiBlOHS proc= h ess-for the esterification'of cellulose irr'whichthe: recovery of the individual ingredients isfacilitated.

The broad idea of =employing a homogeniz'er I in conjunction with asaturated-hydrocarbon in v the fibrous-esterification oi cellulose istheinven- "tion of Minsk, Kenyon and Gray andis disclosed and claimed intheir" application" Serial No. 671,9003'fi1ed of even date. We'havefound that if certain chlorinated hydrocarbons are employeda-fib'rousesterification bath' in which a satu o ratedhydrocarbon isthenon-solvent, the sepa= ration and recovery of thejingredients offth'espent esterifi'cation" bath" is" greatly facilitated. We have foundthatthe halogenated hydrocarbons are especially suitable' as homogenizers:in fibrous esterificationprocesses; as they may re-' plaoeether fatty.vacidxordinarily employed in diam,- esterification mixtureandrtheyoformganeazeo- J tropic1constants:boilingamixture with::-water.We have found that by ourlinyention; manyrrofithe diflicult and. oftenunsatisfactory methods of recovering the ingredients of a spent fibrousesterification bath are eliminatedzwhich have :beenheretoforerthoughtinecessary-xor atrleast prefer-:- able insucht'recoveryn Inna fibrous:esterification process .inxwhich'a 10 :1

saturated hydrocarbonaisremployed-v as the nonsolvent, a surprisinglysmalh amountiofx that hy-: drocarbon is necessary to :rendertheesterification bath nonesolvent I of ithelcellulose ester: formed,

in'fact, thenon solvencyof this-liquid is sorpro- 15 nounced: that'it*extendswven to the constituents of: 'the esterification bath; By the:present invention: the effectiveness of the saturated hydrocarbon te-induce non-solvency of the cellulose ester" by-theesterificatiombath-"may be utilized and an even esterification of the cellulose may beassureds p The-halogfenated hydrocarbons when employed as homogenizersalso present'other advantages in additiontcthose -pointed outabove. Manyof themare inflammability reducing agents whichfeature-is--very"valuab1e:in case of the more vola-, tile: hydrocarbons:such as gasoline: or the like; For "instance: a mixture of ""parts oftrichlorethylene and EOparts'of Stoddard solvent is total- 1ynon-inflammable. Even in ,the case of a halogenated hydrocarbon suchasethylene chloride which will burn; that material-hasa-.comparativelylhighcfiash point soithat the-dangerzof ignition is muchless:comparedowithsome of the othershomogenizers which? might beemployed. The halogenated hydrocarbons are excellent 501- vents-.fortheingredients of the esterification bath and 'in. the case: ofesome ofthese hydrocarbons suclrasethylene vchloride the amount required forhomogenizing: is less than that required when using someotherhomogenizing liquid. We have found that ethylene chloride;propylene chlorideand'trichlorethylene are the most satisfactory in our"invention however "other chlorinated hydrocarbons such -asmethylenech1oride, -carbon tetrachloride, chloroform or other halogenatedhydrocarbons "may; be employed with marked success. The bromide,-iodijde-- and fluoride compounds which correspond to the chlorinated;hydrocarbons-would also be suitable for-homogenizing esteri-ficationbaths which wouldotherwise be heterogeneous.

Our process comprises the esterification of. cel-. lulose izra bathcomprisinga fatty acid anhyformed, by centrifuging. The cellulose esternow contains less than an equal weight of liquid which consists of thenon-solvent, the chlorinated hydrocarbon, a small quantity of fatty acidand the catalyst. The ester is then placed in a vessel adapted for steamdistillation and water andv a sufficient quantity of sodium carbonate toneutralize the catalyst is added. The chlorinated hydrocarbon and thenon-solvent may be removed by steam distillation. The quantity of fattyacid remaining is negligible and may be economically discarded. Theester is washed with water to remove the fatty acid and sodium' salt andmay then be dried.

The following examples illustrate processes which embody our invention:

Example I 30 lbs. of cotton linters were added to a mixture of 90 lbs ofStoddard solvent, 90 lbs. of acetic anhydride, 120 lbs. of ethylenechloride and 810 c. c. of a catalyst consisting of 3 parts by volume ofphosphoric acid and 1 part by volume of sulfuric acid all at atemperature of F. The mixture was stirred occasionally and thetemperature in the jacket of the reaction vessel was raised uniformly toa temperature of 120 F. over a period of 4 hours. The mass wasmaintained at that temperature until a washed and dried sample takentherefrom showed solubility in a mixture of parts of chloroform and 15parts of ethyl alcohol by volume. This usually requires 10-15 hours.

The fibers were then separated from the main portion of the reactionliquid by centrifuging. The remainder of the reaction liquid was removedfrom the fibers by adding water containing sufiicient sodium carbonateto neutralize the catalyst, steam distilling out the ethylene chlorideand Stoddard solvent and washing out the remaining acid with water. Theproduct which was a cellulose triacetate was dried in the usual manner.7

Example II 30 parts of cotton linters were added to a solutionconsisting of lbs. of Stoddard solvent, lbs. of propylene chloride, 60lbs. of 85% acetic anhydride, 45 lbs. of 94% propionic anhydride and 200c. c. of sulfuric acid as the catalyst, all at a temperature of 70 F.The temperature in the jacket of the reaction vessel was raiseduniformly to 120 F. over a period of 4 hours andthe temperature wasmaintained at this point until the product was soluble in a mixture of90 parts of ethylene chloride and 10 parts of methyl alcohol by volume.The product, cellulose acetate propionate was processed as in thepreceding example to remove the reaction liquid therefrom.

Although the present invention will be ordinarily applicable to fibrousprocesses in which the petroleum distillates are employed as thenonsolvent, it is obviously applicable to the use of any non-solventwhich renders the esterification bath heterogeneous thus necessitatingthe presence of a homogenizer to assure an even esterification. In theseprocesses the fatty acid ordinarily employed may be entirely replaced bythe halogenated hydrocarbon in accordance with our invention however ifdesired this substitution of halogenated hydrocarbon for fatty acid maybe only parrtial and the process would still fall within the scope ofour invention.

It is to be understood that our invention is directed broadly to thepreparation of organic acid esters of cellulose although as the simpleand mixed esters of cellulose containing acetyl, propionyl and butyrylgroups are more common at the present time, our invention is moreparticularly directed to the preparation of cellulose esters containingone or more of those lower fatty acid groups.

We claim as our invention:

1. A process for preparing an organic acid ester of cellulose in fibrousform which comprises reacting upon the cellulose with an esterifyingbath containing a liquid petroleum distillate which is essentiallywithin a boiling range of 40-210 C. as the non-solvent and a halogenatedhydrocarbon, in sufficient amount to assure compatibility of theingredients'of the bath, which bath will not dissolve the ester formedtherein.

2. A process for preparing an organic acid ester of cellulose in fibrousform which comprises reacting upon the cellulose with an esterifyingbath containing a liquid petroleum distillate which is essentiallywithin a boiling range of'40-210" C. as the non-solvent and achlorinated hydrocarbon, in sufficient amount to assure compatibility ofthe ingredients of the bath, which bath will not dissolve the esterformed therein.

3. A process for preparing an organic acid ester of cellulose in fibrousform which comprises reacting upon the cellulose with an esterifyingbath containing a liquid petroleum distillate which is essentiallywithin a boiling range of 40-210" C. as the non-solvent and achlorinated olefine, in sufficient amount to assure compati- 5 bility ofthe ingrediets of the bath, which bath will not dissolve the esterformed therein.

.4. A process or preparing an organic acid ester of cellulose in fibrousform which comprises reacting upon the cellulose with an esterifyingbath containing a liquid petroleum distillate which is essentiallywithin a boiling range of 40-210" C. as the non-solvent and an alkylenechloride, in sufficient amount to assure compatibility of theingredients of the bath, which bath will not dissolve the ester formedtherein.

5. A process for preparing an organic acid ester of cellulose in fibrousform which comprises reacting upon the cellulose with an esterifyingbath containing a liquid petroleum distillate which is essentiallywithin a boiling range of 40-210 C. as the non-solvent and ethylenechloride, in suflicient amount toassure compatibility of the ingredientsof the bath, which bath will not dissolve the ester formed therein.

6. Aprocess for the preparation of cellulose acetate propionate infibrous form which comprises reacting upon the cellulose with a bathwhich contributes acetyl and propionyl groups to the cellulose andcontaining a liquid petroleum distillate which is essentially within aboiling range of 40-210 C. as the non-solvent and an alkylene chloride,in sufficient amount to assure compatibility of the ingredients of thebath, which bath will not dissolve the ester formed therein.

'7. A process for the preparation of cellulose acetate propionate infibrous form which com- 75 prises reacting upon the cellulose with abath which contributes acetyl and propionyl groups to the cellulose and.containing a liquid petroleum distillate which is essentially within aboiling range of 40-210 C. as the non-solvent and ethylene chloride, insuflicient amount to assure compatibility of the ingredients of thebath, which bath will not dissolve the ester formed therein.

8. A process for preparing an organic acid ester of cellulose in fibrousform which comprises reacting upon the cellulose with an esterifyingbath containing a liquid petroleum distillate which is essentiallywithin a boiling range of 40-210 C. as the non-solvent and propylenechloride in suflicient amount to assure compatibility of the ingredientsof the bath, which bath will not dissolve the ester formed therein.

9. A process for preparing an organic acid ester of cellulose in fibrousform which comprises reacting upon the cellulose with an esterii'yingbath containing a liquid petroleum distillate which is essentiallywithin a boiling range of 40-210 C. as the non-solvent andtrichlorethylene in sufficient amounts to assure compatibility of theingredients of the bath, which bath will not dissolve the ester formedtherein.

CARL J. MAIM. CHARLES L. FLETCHER.

